Tuyere punches and like machines



.Jan. 26, 1960 w. J. DE VlLLlERS ETAL 2,922,175

TUYERE PUNCHES AND LIKE MACHINES Jan. 26, 1960 w. J. DE VILLIERS HAL2,922,175

TUYERE PUNCHES AND LIKE MACHINES Filed Dec. 11, 1956 TIME STROKE 6Sheets-Sheet 2' Jan 26, 1960 Filed Dec. 11. 1956 W. J. DE VILLIERS ETALTUYERE PUNCHES AND LIKE MACHINES Jan. 26, 1960- w. J. DE VILLIERS ETAL2,922,175

' TUYERE PUNCHES AND LIKE MACHINES 6 Sheets-Sheet 4 Filed Dec. 11, 1956Jan. 26, 1960 w J DE v s ETAL 2,922,175

TUYERE PUNCHES AND LIKE MACHINES Filed Dec. 11. 1956 r 6 Sheets-Sheet 5Jan. 26, 1960 w. J. DE VILLIERS ETAL 2,922,175

TUYERE PUNCHES AND LIKE MACHINES Filed Dec. 11, 1956 v 6 Sheetg-Sheet 6United rates Patent TUYERE PUNCHES AND LIKE MACHINES Willem Johannes DeVilliers and Denis Bruckman, Kitwe,

. Northern Rhodesia Application December 11, 1956, Seriai No. 627,604

Claims priority, application Union of South Africa December 12, 1955Claims. (Cl. 15-104.16)

This invention relates to tuyere punches of the kind used to clear fluidpassages leading into a mass of molten material in a furnace such as acopper converter.

The most widely used practice in punching tuyeres during the operatingcycle of a copper converter involves the use of manual labour. Thetuyeres are provided with "ball valves. These are displaced by theinsertion of a punch rod which is manually reciprocated to clear thetuyere passage. Thus on each converter a number of manual labourers arerequired.

It has been proposed to replace manual labour with mechanical devices.One such device consists in a pneumatic punching machine arranged totravel from hole to hole like a manual labourer. The disadvantage hereis that a furnace seldom keeps to its original shape and that the liningup procedure maybe very difficult. In another arrangement a pneumaticmachine is mounted at each tuyere. In this case it has been found thatthe machine operates satisfactorily except at some plants where the slagencountered seems to be of too refractory a nature for existingmachines.

A big drawback of pneumatic machines is that'constant preventativeservicing is necessary and that maintenance costs are high. In fact themaintenance and servicing personnel may be as large as the labour forcerequired for manual punching.

An object of the invention is to provide a machine which allows offaithful service over relatively long periods and which is automatic toa relatively large extent.

Ina machine according to the invention a tuyere punch rod is actuated bymeans of an armature to which a magnetic force is applied at leastduring the working stroke of the rod. Preferably magnetic forces areapplied to the armature on both the working and return strokes of thepunch.-

Conveniently the magnetic force is applied by means of one or moresolenoids (which are preferably iron clad) through which the armaturepasses. In order to achieve the long stroke necessary, there willusually be at least two solenoids. In the latter case current is appliedto one solenoid to start the working stroke and move the armature intothe sphere of influence of the next solenoid and the current is switchedfrom the first to the next solenoid while the armature is moving atspeed.

Optimum operating efliciency is obtained where the active length of thearmature lies between 1.5D+K and 2D+K, where D is the distance betweenthe pole pieces and K is a design constant.

The invention also provides that the armature is built into or formspart of the punch rod.

In the preferred form of the invention the armature length extendingbeyond the pole pieces of any one solenoid when the armature is inmid-position between the pieces is formed to provide a magnetic path ofreducing cross-sectional area as the ends of the armature areapproached. As a result the armature continues to exhibit thmst afterthe longitudinal air gap between a pole piece and the armature hasclosed. Thus the leading end of the armature is extended into the sphereof influence of the adjacent solenoid. I

To provide the path of reducing cross-sectional area the armaturcistapered and preferably by forming conical indentations at its ends. Theangle of slope has not been found to be critical and in any case theangle is dictated by design considerations.

With the small space usually available behind tuyeres, it is essentialto keep the solenoid dimensions as small as possible. The result is thatthe solenoids handle large currents for small periods of time. Thesupply and control of such currents is of prime importance. It has beenfound that the supply should be in the form of pulses of the requiredduration and properly phased to give the required thrustcharacteristics. At the current levels and switching speeds involved,mechanical switches will not have a long life and for that reason it ispreferred to control the current supply electronically. v

With two coils it is necessary to have a pulse to start movement underthe action of the first coil, a pulse in the second coil to take overfrom the first and also to act as a braking force at the end of thestroke and a third pulse to the first coil to return the rod to itsstarting position. The invention provides in this case that the coils befed from two separate supply lines each of which carries the requiredpulses. Although it is possible to achieve this pulsing byelectromagnetic or electronic chokes in a three phase alternatingcurrent supply, it is preferred to use direct current with twoelectronic rectifiers having a common return.

Grid biased rectifiers give the best result, the grids being normallybiased to prevent current from flowing and the bias being liftedaccording to the current pulses required to work the solenoids. Thelifting of the grid bias is controlled by electronic timing circuitswhich also control the switching to the various punching machines in aseries.

The invention is further discussed hereunder by way of example withreference to the accompanying drawings,

Figure 3 is a graph showing. armature movements inthe configuration ofFigure 2 Figure 4 is a wiring diagram showing the power supply circuitof the machine;

Figure 5 is a block diagram showing the various electrical circuits;

Figure 6 is a circuit diagram of an arrangement for generatingtriggering pulses for the power circuit;

Figure 7 is a circuit diagram of the master timing circuit;

Figure 8 is a circuit diagram of the distribution circuit;

Figure 9 is a circuit diagram of an addition to the timing circuit, and

Figure 10 is a circuit diagram of an ancillary circuit.

The machine shown in Figure 1 and its associated circuitry have beendesigned for use on the tuyeres of a copper converter. The converter hasa horizontal line of about fifty tuyeres the centres of which are spacedat six inches so that the maximum outside diameter of each punchingmachine is 5.75 inches.

Basically the machine consists in two coils 11 and 12 housed in mildsteel barrels 13 separated by a mild steel disc 14 which provides acentre pole piece. The ends of the barrels are closed by mild steelplates 15 and 16 (the end pole pieces) which support Phosphor bronzebushes 17. These bushes act as the bearings and guides for a compositeplunger 37 comprising an armature 18 of soft iron which is cone-spigotedon two pieces of nonrest.

magnetic stainless steel 19 and 2% by means of a high tensile steelscrewed stud 21, and a punching section 22 securedto the front end ofthe piece 20. The section 22 7 is secured by means of a ball and. socketconnection 23 so that the section 22 has a limited degree of play to afollow distorted tuyere pipes and to. be pulled loose when At the rearthe piece 19 has a recessed screwed member 24 which providesan annularprojection 25. The

piece 19 moves in a rear cover 26 which is adapted to telescope .on apipe 27 projecting from the pole piece 15.

' Thear'rangement is such that the projection 25 clears the'pipe 27'andabuts against the pole piece 15. At the rear of the pipe 27 there is acap 28 providing an annular recess 29 having a sloping wall convergingforwardly towards the axis of the punch rod. A ball 30 is housed:

in the recess .29. g

If the machine is moved out of its normal working plane, 'e.g. to tiltthe furnace, in the direction of the arrow 31, the ball rolls down thesloping recess 29 and obstructs the projection 25 (see Figure 1) thuspreventingthe, punch rod from moving into the cavity of the furnace .Atthe. same time the telescopic cover 26 moves down" until its backcontacts the cap28. The total clearance of the machine while tilting isthus considerably aperture 35 The plunger 37 is actuated by means of thetwo coils Hand 12. The magnetic circuit involved is diagrammaticallyillustrated in Figure 2. As shown the armature 1 8 is at its startingposition relatively to the rear pole 15. The'dotted line positions arepositions relatively to the other poles 14 and 16 of the front end 40 ofthe arma ture 18.

- The firstpoint to be noted in connection with the magnetic circuit isthat the length 38 of the armature 18 is between 1.5D+K and 2D+K whereD'is the distance between the centres of the pole pieces 15 and 14 andfKis a design constant. The distance between the centres of, the polepieces 14 and 16 is larger than D for reasons indicated below, but inthis case also the equation should be satisfied, with the sameconstantjK and D1 being the distance between the poles 14 and 16 thelength'38 of the armature 'must lie between l.5D1+K and 2D1+K.

. Assuming that current be applied to the coil 11 then movement of theleading end 4410f the armature 18 in relation to time is shown in thegraph 41 plotted in Figure '3. At about the point 42 (corresponding todotted line position 42 in Figure 2) the armature will come to It nowthe coil 11 is de-energised and the coil 12 fed with current, the curve43 represents further'movement of the armature '18. The punching strokeis achieved by a combination of the curves 41 and 43 to the form shownin the curve 44, i.e. an almost sinusoidal stroke may be achieved. Thestroke shown in curve 44 is attained by switching off the current incoil 11 when the leading end 40 has passed'the pole piece 14 (e.g. atpoint 45) and applying current to the coil 12.. The amplitude of theoscillation will be larger than for coil 7 11 becausethe armaturepossesses the combined kinetic Y depend on the starting point, thedistance between pole pieces, the overshoot of the plunger and thetiming of the switching. v I

In practice the switching will'be determined by the dynamic response ofthe machine. The overshoot has been found to depend on the depth of theconical indentations 48 and the starting point may be chosen at willwithin limits. Thus the stroke of the a question of geometry. r

The actual length of the coils is determined by the current loading andthe desired length of the power stroke. The maximum displacement beingdependent only on the length of the armature, the depth of the cone andthe starting point, the percentage of the total stroke under powerdepends on the length of the coil 12. To ensure that at least 75 percentof the plunger stroke is under I to the coil 11 by about one third.

, to space limitations the coils are relatively small and Any suitableform of switching may be used, but there are several important factorsthat have to be taken into consideration. Firstly the current pulsesapplied to the coils must be very accurately controlled. Secondly dueextremelylarge current densities (of theorder'of 1500 amps. per squarecentimetre) are involved. The basic switching problemis then to handlelarge power pulses for very short but well-defined periods and to ensurethat the loading'on any one coil is not repeated too often.

- By using grid-controlled mercury arc rectifiers the switching problemsare simplified to a large extent. The rectifiers serve the functions ofconverters and contactors. As said above, the use of direct current ispreferred for the reason that suitablemagnetic materials for the use ofalternating current are not easily available.

Figure 4 showsa circuit which was devised to-use mercury arc rectifiersof the kind made by the English Electric Company and known as excitrons.'In this -circuit six excitrons 49 have been arranged in sets of three,

each set feeding a supply line 50 or 51 and the sets having a commonreturn 52 in a well known manner. Briefly all the cathodes of theexcitrons 49 are connected 'to the common return 52. The anodes in a setare connected to a secondary 54 of a double wound three phase transformer 53;

In addition to grid control the excitrons have dipping anodes SS forstriking the arcs.. Both grid and excita-- tion voltages are provided byseparate rectifiers 56 from transformer secondaries-57. Thedippinganodes are extracted by' excitation chokes 58. Resistances 59 areon-load current limiting resistances and 60 are stabilising resistances;'Grid limiting resistances 61 and loading resistances 62 for pulsetransformers are alsoprovided.

The excitation currentis interrupted by contact 71 in a manner to .bedescribed later on. r a

The arrangement is such that the grids of the ex citrons are normallysufiiciently' biased to prevent the tubes from firing even if thedipping anodes are extracted.

. The transformers 70 are arranged to providetriggering pulses (by meansto be discussed later on) synchronised with the main supply" and phasedto trigger the excitrons off as the voltage on their anodes rises in thepositive direction. r

The overall circuit arrangement is shown in Figure 5 where 72represents. the power circuit such as that discussed with reference toFigure 4, 73 represents the pulse generator for providing incipienttriggering pulses, 74. 7 represents a timing circuit, '75 a distributioncontrol cir cuit, and 76 and 77 ancillary circuits; In this scheme thecircuit 73 continuously produces trigger pulses, syn-' chronised to themain supply. The timing circuit 74 is arranged to provide gating pulsesto the circuit 73 to allow only some of the incipient trigger pulses topass and become trigger pulseswhich actuate the excitronsin the circuit72. The timing circuit is also interlocked machine is largely with adistribution circuit 75, so that gating pulses are only generated whenthe distribution circuit is in order and so that the distributionconnections are made relatively in phase with the gating pulses. Thecircuit 76 is arranged to act manually or automatically to allow thedistribution circuits to operate as and when punching strokes aredesired or required. The circuit 77 is arranged to'interrupt thedistribution circuit when certain predetermined outside conditions arenot satisfied or when manually operated for maintenance or otherpurposes. The circuit 75 also includes a relay which is adapted to closethe contacts 71 in the circuit 72.

If the frequency of the main alternating current supply is at fiftycycles, the frequency of the trigger pulses from the circuit 73 must beat 150 cycles per second. The gating pulses are conveniently of such anature that the line 50 carries power pulses suitable to energise thecoils 11 of a series (say fifty) of punching machines.

The line 51 carries the pulses necessary to work the coils 12 of theseries. The sequence is then a pulse on line 50 to start an armature 18moving, a pulse on line 51 to continue such movement and return thearmature toward the first coil and finally a pulse on line 50 to movethe armature back to its starting position. While the circuit 75switches over to the next punching machine there is an interval duringwhich neither line 50 or 51 carries any pulses. At the end of a salvo,i.e. when all the machines in a series have been operated to punch,there may be a predetermined delay or the circuit 76 could take over. Itis, however, essential that the three power pulses must follow eachother in sequence to ensure that a punch rod returns to its startingposition and the circuit 77 is therefore so arranged that it can onlyinterrupt a salvo at the end of a set of three power pulses to the samemachine. The circuit 75 operates power contactors 78 which close thecircuits to the solenoids 11 and 12 just before a set of power pulses isdue to arrive and open them just after such power pulses haveterminated.

Numerous detailed circuit arrangements are possible to achieve thegeneral conditions outlined above. Figure 6 illustrates a circuitsuitable for generating the incipient trigger pulses. A separate threephase secondary winding 79 is wound on one of the excitationtransformers 57 (Figure 4) and feeds a bank of star connected germaniumdiodes 80. The ripple voltage superimposed upon the rectified voltage isapplied inverted to the grid of a triode 81 which modulates a unistableflip-hop c1rcuit comprising triodes 82 and 83. This circu1t is adjustedto pass square waves of a time duration depending on the value of thegrid resistance 84. The 150 cyclesper second ripple voltage locks theflip-flop to the third harmonic of the mains frequency. I

The resultant square wave pulse is differentiated in the circuitincluding condenser 85 and resistance 86, so that its trailing edgedevelops a positive going pip the phase of which in relation to theripple pulse is controlled by a variable resistance 87.: These positivegoing incipient trigger pulses are applied through condensers 88 to thegrids of a pair of power amplifiers 89 and 90 to the bias voltage ofwhich is such that they will not normally conduct even in the presenceof the incipient trigger pulses. If the bias is reduced by, say fiftyvolts, the tubes 89 and 90 wil conduct for the period of each incipienttrigger pulse. This bias is controlled by gating pulses from the timingcircuit to be described later on.

The outputs of the amplifiers 89 and 90 are fed to the transformers 70described with reference to Figure 4.

A suitable timing circuit for deriving gating pulses is illustrated inFigure 7. This circuit is well known in the art and fundamentallyconsists in what are known as univibrator circuits. The circuittherefore includes pairs of triodes, the pairs being numbered 100 to104. The members of each pair are so interconected that they pro- 'videa unistable circuit. Normally, i.e. in the stablestate,

the one tube conducts and the other does not. When a negative goingsignal is applied to the grid of the conducting tube (the right hand onein th drawings) its anode potential will rise thus progressivelyreducing the bias of the second or left hand tube until the bias exceedsthe cut-off potential of the second tube. If the input signal issufficiently large in amplitude the second tube begins to conduct. Thisresults in a violent feed back between the tubes causing the grid of thefirst tube to be depressed to the full of the change of voltage on thecondenser between the anode of the first tube and the grid of the secondtube, thus cutting off the first tube and attempting to raise thepotential of the second tube. The pair remains in this condition untilthe charge on the condenser 105 gradually leaks away through a variableresistance 106 and a resistance 107. As soon as the potential of thefirst tube passes the cut-oil. point, violent feedback again results andrapidly restores the circuit to the normal stable state.

The period of the quasi-stable state depends on the supply voltage, theload resistance of the tubes and the coupling time constant of thecondenser105 and the resistance 106 and 107.

As shown the anode of the first tube in a pair is connected to the gridof the first tube of the next pair of the five pairs via a smallcapacitance 108 and a large resistance 109 for the next pair to triggerinto the unstable state as soon as the former pair returns to the stablestate. In this way the pair 100 triggers the pair 101 and so on to thefifth stage 104 which in turn starts the cycle. It should be noted thatthe values of the various resistances are so chosen that a stage cannottrigger any stage beyond the next stage.

The grid voltage of the left hand tube of each of the stages 100 and 103is applied to a potential divider 110 which feeds the grid of the poweramplifier 89 (see Figure 6) with the result that only if the stages 100and 103 are in the unstable state, the tube 89 allows current to passthrough its transformer 70. Likewise the grids of the left hand tubes ofthe stages 101 and 102 are connected to a potential divider 111 whichfeeds the tube 90.

Diodes 112 are provided to prevent paralleling of the grid circuits ofthe timing circuits.

The output from stage 103 is fed to stage 104 which is the intervaltiming stage. The latter is arranged for a much longer quasi-stablestate to provide the time interval for switching from one punchingmachine on to the next. The right hand grid of stage 104 is alsopermanently conected to a negative supply potential through a resistance113 and to ground through a pair of contacts 114. The latter form partof the interlock with the dis- I tribution circuit discussed below. Itshould at this stage be noted that if the contacts 114 are bridged, thestage 104 operates in the normal way. With the ground point removed,this stage is held in the unstable state. By operating the contacts 114gating pulses may be initiated or stopped at will but only in completebatches.

Stage 104 also feeds into a further stage consisting of a single tube115 which works in tanden with it. The tube 115 cuts off with the secondtube of stage 104 to de-energise a relay in the distribution circuit. Assoon as the time delay involved in the circuit including a condenser 116and a variable resistance 117 allows, the relay 120 is re-energised.

Depending on the number and time intervals of the individual timingstages in the circuit, so a wide variety of output pulses may be appliedto the power amplifiers 89 and 90. It has been found in practice thatgood punching results are obtained by arranging stage 100 to gate fivetrigger pulses, stage 101 one such pulse, stage 102 eleven pulses andstage 103 five pulses. The fifth stage 104 is arranged to give a delayto suit the reaction time of the distribution circuits. In eachsituation it is best to determine the correct timing by experiment.

' to ground.

timing circuit. There is also athird relay128 which locks itself toground through contacts 138, closes a pair of contacts 130 and moves acontactor arm 131 from the position shown to a position where it puts aselector 132 in circuit.

The relay 124 is connected to a uniselector the arm 133 of whichsweepsacross a bank of contacts 134 (the first one) and 135 of which there areas many as. there are punching machines. The uniselector 133 and theselector 132 if it is of the traction type are driven by magnets 136.The contact 127 is in circuit with a relay 137 which closes. thecontacts 71 referred to with reference to a Figure 4.

The circuit 76 includes means to complete it for the purpose ofinitiating a salvo or a train. of salvos. The circuit 77 includesvarious means for'interruptin'g a salvo V or a train of salvos.

Starting from the position where the selector arm 133 connects thecontact 134, if the circuits 76 and 77 are completed, the relay 124 isenergised by being connected This relay then locks itself to ground bymeans of the contacts 125 (which it closes) and the contacts 123 whichare normally held closed by the relay 120.. At the same time thecontacts 114 are closed to initiate the timing circuit to start a trainof power pulses. The relay 124 also closes the contacts 127 which bymeans of the relay 137 close the excitation contacts 71. The othercontacts 126 governed by the relay 124 are also closed, but the relay128 remains de-energised as the relay 12% holds the contacts 122 open.

.As the first timing cycle is completed, the relay 120 is momentarilyde-energised and the contacts 122 close to energise. the relay 128, sothat the arm13 i1 moves to connect the selector 132 in. circuit, thecontact 130 is closed in the circuit of the magnets 136 of the selectorson the selectors. If the contact 135 in question is still connected toground via the circuit 77 the next cycle proceeds and so on until allthe contacts |135in the bank have been wiped by the arm 133/ The latternow again proceeds to the contact'134 and if the circuiti76 is now openthe relay 124 which has no ground connection when the relay 12tl ismomentarily de-energised, drops out and punching stops until such timeas the circuit 76 is again completed. if for any reason the circuit 77'is interrupted at any time during a salvo, the relay 124 will act in thesame way, but only at the end of a cycle. The contactor arm 1 31 isinitially connected to a relay 1'29 which when energised actuates a.contactor to connect a dummy load across the lines 50,51 and 52 Thuswhenever the relay 124 has dropped out, at the end of a salvo was aresult of an interruption of a salvo, the dummy load is first connectedto the power supply before punching machines. are connected in circuit.The arms 133 and 131 are prevented from moving as the relay 128 is notenergised. Thus the excitrons 49 have time to settle down before beingcalled upon to operate a punching machine. After the first power pulses,the relay 1 2i 'is' momentarily dia -energised and the relay 128comesinto operation and remains energised as long as the relay 124 isenergised. These lectors 133 and 132 are stepped on by opening andclosing the contacts 121.-

1; In order to ensurethat the line contactors do notopen before theheavy current impulses to the punchingmachine i coils. have terminated,the contacts of the relay are arranged to'have a ten milliseconddelay'on opening. f I

.The circuit 77 includes various means for stopping punching operations.Thusthere may be manual. switches at the'main control room and onstrategic points at the punching site.. Furthermore where airv pressuredrops below a predeterminedminimum it is desirable to stop punchingaltogether. Eorthis purpose a pressure switch operating on this lowpressure is included in the circuit. As it is also undesirable, in thecase. of a rotary converter to punch. during tilting, the circuit alsoincludes a mercury tilt switch on the converter as well as. a limitswitch on the tilting motor brake arranged to open while the motor is inmotion. Any of these switches will immediately stop the next punchingcycle and a salvo will be completed only if the stop circuit 77 is againcompleted.

For initiating a salvo a timing clock maybe arranged to operate thecircuit 76. A suitable arrangement is shown in Figure 10. In this casesalvo frequency is determined. by overall air flow to the tuyere.Differential pressure switches 140, 141 and. 142 are-arranged to beresponsive to different minimum volumes of air flow and on such minimumflow being reached each allows a pair of contacts 143, 144 and 145respectively to close. The

spring contacts 146 which are'helcl open bycams 147, 1'43 and 149. Thecamshavenotches to allow closing of the contacts 146' depending on thespeed at which the cams are rotated by the motor of a timing'clock. Ifthe switch 140 allows the contacts '143 to close, the overall initiatingcircuit by means of thecam 147; with four notches will be. closed fourtimes per revolution of the motor 150; Theswitch 1 41 and" the cam'148closes the circuits twice and the switch 142 and the cam 149 once only.V j v i Thus the camsin sequence initiate a lesser number of salvos perrevolutionof the motor 150 untilgat a predetermined maximum flow thepunching machines remai inoperative. V g

- It has been 'found that there is a dip in the. back developedby thecoils 111and1'2, as they are."

straddled by the armature 18. p This fact may be utilised forautomatically switching the coils. j 'A" suitable circuit is illustratedin Figure 9. In'thiscase thecoil (say 11),

is connected to the .power. supply lines 50 and ,52 through a resistance151. .Two further rmista nces 152and 153 are connected between .thelinesin'series with one another andin parallel with the resistances 1 1 and151.

The ratio ,of the resistance of the coil 11. to the reistance 151 is thesame as that of the reistance 153 to the resistance 152. The centrepoint between the resistances 11 and 151 is connected to a coincidencediffer ential circuit comprising'a high tension supply, a limiting backof a predeterrnined magnitude takes place.

a pulse having the voltage of the coincident circuit differential isformed at 161, This pulse may be injected at point 162, in Figure 7 inorder to step the timing sequence on. If. this circuit is used thetiming circuits areset at longer intervals than usual, but these wouldbe automatically shortened-by the back characteristic.

A similar circuit could be used for coil 12 and the resulting pulseinjected at a point such as 163. In this case the timing circuit of thepair of triodes 101 must gate that portion of the pulse which performsthe forward stroke in coil 12 and the timing circuit of the pair oftriodes- 102 must control the return stroke.

By using the circuits of Figure 9 the velocity of the plunger 37 ismaintained at a maximum level. 'Furthermore if an encrustation isencountered in a tuyere pipe the machine automatically adjusts itsstroke to suit the free length of the tuyere pipe, In other words themachine automatically assesses the conditions encountered by the plunger37 and adjusts the power pulses accordingly.

Instead of the timing circuit shown in Figure 7, a circuit employingdekatron tubes may be used. In this case the pips developed in thecircuit of Figure 6 are fed to the grids of the dekatron tubes andrequired groups of dekatron cathodes are connected to the grids of thepower amplifiers 89 and 90. Dekatron tubes may also be used as theselector 132 (Figure 8) and in this case the power to the linecontactors 78 is supplied by thyratron tubes the grids of which areconnected to the dekatron cathodes.

The punching machine provided by the invention gives satisfactoryservice under most dificult conditions. A stroke as long at 12.5 incheshas been maintained with the machine.

We claim:

1. Tuyere punching apparatus including a series of punching machineseach of which has a punch rod, an armature of magnetic material formingpart of the punch rod, and a forward and a backward solenoid surroundingthe path of the armature, the armature comprising a main portion ofsubstantially uniform cross-sectional area and hollow tapering ends ofsufficient length so that by means of the continual increase ofcross-sectional area after a solenoid has been bridged, the armaturecontinues to have thrust in the direction of its leading end and whilecurrent is flowing in the first solenoid; including two current supplylines, a common return to the supply lines, means to switch any onemachine from the series to the supply lines so that when a machine isthus switched the backward coil is connected to the first line and theforward coil to the second line, means to supply current pulses to thesupply lines after a machine has been switched to the lines, the currentpulses being such that a first pulse in the first line causes thebackward solenoid to move the armature from a starting position into thesphere of action of the forward coil, :1 second pulse in the second linefollows the first pulse immediately to cause the forward solenoid tomove the armature to the end of the working stroke of the rod and toreturn the armature into the sphere of action of the backward coil and athird pulse in the first line follows the second pulse immediately tomove the armature back to its starting position, the switching meansbeing arranged to connect the machines to the lines in turn,

2. The apparatus claimed in claim 1 including two groups of grid biasedpower rectifiers connected to an alternating current supply, one groupbeing connected to the first line and the other to the second line, andmeans to generate trigger pulses to lift the bias of the grids to thepower rectifiers in phase with the required supply current pulses.

3. The apparatus claimed in claim 2 including a pair of secondary gridbiased rectifiers for supplying the trigger pulses to lift the bias ofthe grids to the power rectifiers, means for generating incipienttrigger pulses in phase with the alternating current supply of the powerrectifiers, the incipient pulses being so phased that if they were ofsufficient amplitude to allow the members of the rectifier pair toconduct, trigger pulses for each half cycle of the alternating currentsupply would be provided, but being of insufiicient amplitude to liftthe bias of the grids of the pair sufiiciently for the pair to conduct,and means to generate gating pulses interlocked with the switching meanswhich added to the incipient trigger pulses allow the members of thepair of conduct and to provide a predetermined pattern and number oftrigger pulses to the power rectifiers.

4. The apparatus claimed in claim 3 in which the gating pulses are sointerlocked with the switching means that each machine is switched tothe lines before the first power pulse arrives and disconnected from thelines after the third power pulse has terminated.

5. The apparatus claimed in claim 4 including a stop circuit soconnected with the gating pulse generating means that on the stopcircuit being open the gating pulse generating means only suppliesgating pulses to operate that machine which is then connected to thelines to the position of rest of the armature.

6. The apparatus claimed in claim 4 including means sensitive to theflow of air to the tuyeres to cause the gating pulse generating circuitto operate.

7. The apparatus claimed in claim 1 in which the switching means and thecurrent supply means are so interlocked that each machine is switched tothe lines before the first pulse arrives and disconnected from the linesafter the third pulse has terminated.

8. In combination a series of identical linear electric motors each ofwhich has a thrust arm, an armature of magnetic material forming part ofthe arm, at least two solenoids surrounding the path of the armature,current supply lines equal in number to the number of solenoids in amotor, a common return for the supply lines, means to switch any onemotor of the series to the supply lines so that its solenoids areconnected to the lines in a predetermined sequence common to all motors,means to supply current pulses to the supply lines after a motor hasbeen switched to the lines, the current pulses being such that a firstpulse in the first line causes the backward solenoid to move thearmature from a starting position into the sphere of action of anadjacent solenoid, following pulses in the other lines follow the firstpulse and one another immediatelyto cause the adjacent solenoid andfollowing solenoids to move the armature towards the end of the thruststroke of the arm and the pulse to the forward solenoid acting also toinitiate movement of the armature in the reverse direction, pulsesfollow in reverse order and the final pulse to the backward solenoidmoves the armature back to its starting position, the switching meansbeing arranged to connect the motors to the lines in turn.

9. In combination a series of identical linear electric motors each ofwhich has a thrust arm, an armature of magnetic material forming part ofthe arm, two solenoids surrounding the path of the armature, a currentsupply line for each solenoid, a common return for the supply lines,means to switch any one motor from the series to the supply lines sothat its solenoids are connected to the lines in a predeterminedsequence common to all motors, means to supply current pulses to thesupply lines after a motor has been switched to the lines, the currentpulses being such that a first pulse in the first line causes thebackward solenoid to move the armature from a starting position into thesphere of action of the forward solenoid, a second pulse in the secondline follows the first pulse immediately to cause the forward solenoidto move the armature to the end of the working stroke of the armatureand to return the armature into the sphere of action of the backwardcoil and a third pulse in the first line follows the second pulseimmediately to move the armature back to its starting position, theswitching means being arranged to connect the motors to the lines inturn.

10. Tuyere punching apparatus including a series of identical punchingmachines each of which has a punch rod, an armature of magnetic materialforming part of the punch rod, at least two solenoids surrounding thepath of the armature, current supply lines equal'in number to the numberof solenoids in a machine, a common return for the supplyrlines, meansto switch any one machine of thefseries'to the'supply lines so that itssolenoids are connected to the lines in a predetermined sequence commonto' all machines, means to supply current pulses to the supply linesafter a machine has been switched to the linesfthe currentvpulses beingsuch that a first pulse in the first line causes the backward solenoidto move the armature from a starting position into the sphere of actionof an adjacent solenoid, a following pulse in another line follows thefirst pulse immediately to cause the adjacent solenoid to move thearmature towards the ,end of the Working stroke, and a pulse inthe lastline connected to the forward solenoid follows immediately on the pulsefor the solenoid adjacent the forward solenoid to cause the forwardsolenoid to move the armature to the end of the working stroke of therod and to reverse the directio'n of movement of the armature, pulsesare fed to the solenoids in reverse order to the working stroke and thefinal pulse V 12 to the backwards fsolenoid moves the armature backtoits starting" position, the switching means being arranged to connectthemachines tolthe'lines in'turni f v 1 References Cited in the file ofthis patent UNITED STATES" PATENTS $07,671 Boekl'en Oct, 31, 1893637,809 Meissne'r Nov. 28, 1899 1,819,008 Weyandt Aug. 18, 19311,999,640 Royse Apr. 30,1935 2,008,795 Olmstead July 23, 1 935 2,182,0141" Clark Dec. "5 1935' 2,344,758 a Welsh 'Mar. 21, 1944 2,429,581-Maitlen Oct. 21,1947 '2,640,955 Fisher 7 JuneZ, 1953 2,664,161 SchlechtDec. 29, 19:53 "2,686,280 I Strong et'al Aug. 10,1954 2,696,979 Berg

